LCD displays are widely used in TVs, laptop computers, PCs, mobile phones, and other electronic products having display function. In an LCD display, cold cathode fluorescent lamp (CCFL), field-effect light-emitting device (EL), light-emitting diode (LED), or other elements capable of emitting a visible light are used as a backlight. In recent years, LED has gradually become a preferred backlight source instead of CCFL because of its various advantages including: long lifetime (about 100,000 hours), capability of optimizing color gamut, small size/design flexibility, low-voltage power supply driven, short turn-on time, no inverter needed, efficiently operated over a wider temperature range and so on.
An LED backlight device generally comprises an LED matrix for providing an LCD panel illumination. In order to make the LCD panel be illuminated with uniform light, and prevent the LCD panel illuminated with bright spots, using a lens to refract the light from an LED is the mainly solution in prior arts. Therefore, in the LCD display using LEDs as backlight source, the way to enhance the uniformity of brightness or make the light distribution be wider is the main issue for improving the LED backlight device. For example, U.S. Pat. Nos. 7,348,723, 7,963,680, 7,621,657, 7,798,679, 7,866,844, 7,766,530, US Patent Publication No. 2009/0116245, U.S. Pat. Nos. 7,474,475, and 7,746,565, all disclose lenses or LED devices designed for an LCD panel.
A light beam from an LED chip has peak intensity (in unit of candela) at an optical axis of the LED chip, and weaker intensities with the greater the included angle between the light beam and the optical axis. Due to the above feature, conventional light source devices are improved for better light uniformity by many kinds of optical lenses each having a light emitting surface and/or a light incident surface with enhanced refractive power to reduce the luminous intensity of a paraxial region of the light source device, and compensate said luminous intensity to a far-axis region of the light source device. As a result, a Fresnel's reflection phenomenon tends to be generated on the light emitting surface, thereby decreasing the total flux of the light source device. Therefore, a light control lens that is capable of distributing light beam evenly as well as increasing the light utilization efficiency is needed for solving light loss because of partial reflection at the light emitting surface of the conventional light source devices.